1. Field of the Invention
The present invention relates to a method for detecting leaks in welds securing a first annular conduit to a second annular conduit wherein the conduits are attached to one another by a pair of annular welds with a chamber therebetween, the chamber being formed by the overlapping of the conduits. More particularly, this method relates to testing for leaks in welds securing a wellhead to a caisson on which the wellhead is mounted by introducing heated oil into a chamber between a pair of annular welds which secure the wellhead to the caisson. This invention also concerns an apparatus for introducing heated fluid into the chamber for testing for leaks in the welds.
2. General Background
In the drilling of oil and gas wells, a caisson is placed into the ground through which oil and gas travels to the surface of a land formation or body of water. A wellhead is conventionally placed on top of the conduit for controlling the flow of liquid, and is secured to the caisson by welding. Typically, the wellhead has an inner diameter portion which is greater than the outer diameter of the caisson, and this enlarged inner diameter portion permits the wellhead to the co-axially aligned and overlappingly disposed around the caisson. The overlapping portion of the wellhead creates an annular chamber between the caisson and wellhead, the chamber having an open annular upper juncture on the interior of the caisson and wellhead, and an open, annular lower juncture on the exterior of the caisson and wellhead. These junctures are each closed by a continuous weld to sealingly engage the wellhead to the caisson. If the welds do not sealingly engage the wellhead and caisson, oil being obtained from the land formation can leak out through the welds.
It has been known in the art to introduce a testing fluid, such as oil, into the chamber between annular welds to determine if the welds will leak when the well is in use. However, introduction of oil into the annular chamber too soon after welding causes cracking of the welds, wellhead and caisson because these parts are heated to at least several hundred degrees by the welding process. Accordingly, it has been necessary to wait several hours before testing the welds. If it were then found that the welds leaked, additional welding would take place, followed by several additional hours of waiting, and then testing again. This time consuming procedure could be repeated ad infinitum until the welds were found not to leak.
It is an object of this invention to provide a method of testing for leaks in the welds securing a wellhead to a caisson without waiting for the welds to cool.
It is still a further object of this invention to provide a method of testing welds for leaks in any pair of overlapping conduits secured to one another by a pair of annular welds having a chamber therebetween formed by the overlapping of the conduits.
It is also an object of the invention to provide a convenient and portable apparatus for introducing heated oil into the chamber between the annular welds for testing the welds securing a wellhead to a caisson.